The present invention relates to a beam position monitor/detector for determining the position and flux of a photon beam, and, more particularly, to a photoconductive type detector having a diamond disk overlaid on both sides with thin layers of conductive material and electrically biased for monitoring X-rays and gamma radiation.
High energy synchrotron radiation sources such as the European Synchrotron Radiation Facility (ESRF) and the Advanced Photon Source (APS) at the Argonne National Laboratory produce brilliant and intense x-rays which is used for research in fields such as material science, chemistry, physics, and medical and biological imaging. Essential to the proper operation of such radiation sources is the ability to determine the position and flux of the x-ray or photon beam with precision and accuracy, so that the beam may be steered and adjusted to provide the desired output beam. Additionally, the monitor must be robust enough to withstand the intense x-ray or photon bombardment which can create extremely high heat loads on certain surfaces.
Prior art beam position monitors (BPM), such as described in U.S. Pat. Nos. 5,387,795 (Kuzay et al.) and 5,404,014 (Shu et al.), have traditionally been of the photoemission type. These monitors typically included blades or windows fabricated of chemical vapor deposition (CVD) diamond cores which are coated or patterned with photon sensitive materials. By measuring the photo-emission current generated when a particle beam impinges on the blades or windows, the position of the beam can be determined.
The BPM described in Kuzay et al. (795) includes a plurality of spaced diamond blades, coated with a photon sensitive metal layer, which are paired and positioned opposite each other about the periphery of the photon beam. By measuring the amount of energy impinging on the blades, the beam position can be determined. Such a monitor, however, is difficult to setup and align and affects the beam that is impinging on the blades.
On the other hand, the monitor/detector described in Shu et al. (014) is a single unit made of a diamond window having metal sensors placed on it in a predetermined configuration. This monitor has the advantage of being easily aligned and can be readily positioned in the path of the beam without significantly affecting the beam being transmitted through the window. However, the photo-emission nature of the monitor requires that a vacuum be maintained for the metal sensors to operate normally. Further, the monitor is not very sensitive to hard x-rays.
Additionally, imaging systems for high energy x-ray beams and other ionizing radiation sources are useful in many industrial, scientific and medical applications, such as in industrial nondestructive testing, biological, radiological and medical studies, etc. Regular charge coupled detectors (CCDs) are very sensitive to x-rays and other ionizing radiation and are easily damages when subject to high intensity radiation sources. Therefore, a practical imaging system must be robust enough to sense and detect x-rays or gamma rays without suffering significant degradation. Further, such imaging systems must also be large enough to scan the entire image of a sample or specimen being tested or irradiated.
In view of the foregoing, the general object of this invention is to provide a photoconductive high energy photon beam detector that can precisely measure the position and flux of a photon beam and yet be able withstand the power and energy of hard x-rays and gamma radiation.
Another object of this invention is to provide a photon beam detector that allows a beam to transmitted through the detector without significant interference or resistance.
Yet another object of this invention is to provide a photon beam detector that can operate in a vacuum, as well as in atmospheric conditions.
A further object of this invention is to provide a photon beam detector that is sensitive to hard x-rays.
An additional object of this invention is to provide a photon beam detector that can image an entire sample or specimen being irradiated.
Additional objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.